Steam cut-off valve



2 SheetsSheet 2.

ATTORNEY Patented May 12, 1885.

G. W. ANDERSON.

STEAM OUT-OFF VALVE.

l/VVENTOR I (No Model.)

UNITED STATES PATENT OFFICE.

STEAM CUT- OFF VALVE.

.GPECIFICATIOIT forming part of Letters Patent No. 317,609, dated May 12 1885.

Application filed June 5, 1884. (No model.)

- To all whom it may concern:

Be it known that I, GEORGE W. Annnnson, of NVestport, in the county of'Decatur and State of Indiana, have invented certain new and useful Improvements in Steam CutOff Valves; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

My invention relates to an improvement in steam cutoff valves.

It is well known that as ordinarily constructed the farther a valve travels the faster it travels, and therefore the quicker will it effect an opening and closing of the steamports; but the objection has been that by increasing the length of stroke or outside lap the back-pressure upon the piston has been increased, and hence the advantage of a quick cutoff has been counterbalanced by the disadvantage of the back-pressure.

The object of my present invention is to provide a cut-off valve which shall have a great amount of outside lap, and at the same time admit of a very small amount of backpressure.

WVith this end in view my invention consists in certain features of construction and combinations of parts, as will be described hereinafter, and pointed out in the claims.

In the accompanying drawings, Figure l is a transverse sectional view of the valve with parts in position as the piston is about completing its stroke to the left. Fig. 2 represents the exhaust closed by one section of the movable block in contact with a projection on the valve. Fig. 3 represents the position of parts after a full opening has been effected. Fig. 4 represents devices for preventing the blocks from cutting the valve-seat, and Fig. 5 represents a bottom plan view of the valve.

My invention is particularly adaptable to a cylinder provided with two steanrports and one exhaust-port.

A represents a slidevalve of ordinary construction, provided with depending projections B, extending the entire length of the recess or chamber 0, formed in the under side of valve A. The projections B are provided with flat faces on the sides toward the outer edges of the valve, which faces are distant from each other about the width of the exhaust-port E.

Two movable blocks, D, sufficientlylong and wide to nearly cover the steam-ports F and about onehalf the height of the recess 0;

are rigidly connected at their corresponding ends by bars G. The faces of the blocks D toward the projections B are flat and adapted to engage the flat faces on the said projections and form a steamjoint. The blocks D are secured at such: a distance apart that when one of the blocks is in contact with the projection B the block will be about midway between the other projection, B, and the side of the recess 0. Suppose the piston to bemoving toward the left and just about completing its stroke: The valve A is moving toward the right, and the exhaust over the block D is just about to cease, as shown in Fig. 1. As the valve completes its stroke to the right and is just starting on its return, the steam-port on the left will be wide open and the exhaust free, as noted in Fig. 3. As the valve reaches about its one-half stroke to the left and is about to open the steam-port on the left to the exhaust, the exhaust is closed by the projection B, in contact with the block D, and remains closed by this contact, thus holding the steam on the piston until the proper time for the exhaust to begin, which will be when the block D,in contact with the projection B, passes to the left over the steam-port on the left. This same movement of parts will be repeated as the valve returns to the right. It will be observed that I obtain by this arrangement a great amount of outside lap and consequent quickness of out-off, while the active steam is held upon the piston and the spent steam allowed to escape with almost, if not quite, the same degree of precision as is obtained by very slight outside lap.

To hold the blocks D in contact with the valveseat when the valve is on the side of the cylinder, I introduce spring-rolls H between the tops of the block and the upper surface of the recess or chamber 0. These rolls H are preferably made of coiled wire andheld against displacement by suitable projections, h, on the upper surface of the chamber 0. These rolls also serve to break the joint formed by the contact of B and D when the movement is slow.

The pressure on the blocks D is at times considerable, and they consequently have a tendency to cut the valveseat. To obviate ICQ this I provide the blocks D at or near their outer corners with projecting arms or lugs d, as shown in Fig. 4, forming a tapering recess between the arm at and the top of the block, and further provide the projection B with a tapering tongue, 12, adapted to be received in the said tapering recess, and form a bearing for the block D at the time the pressure upon the block is greatest. These projections,which form the recess and bearings, need to be only threeeighths or one-half inch wide; hence they form no appreciable obstruction to the passage of steam or the action of the rolls H.

It is evident that slight changes may be made in the form and construction of the several parts without departing from the spirit and scope of my invention; hence I do not wish to limit myself strictly to the construction herein set forth; but,

Having fully described my invention, what I claim as new, and desire to secure by Letters Patent, is

1. The combination, with a sliding valve provided with projections depending into the valve-chamber, of blocks adapted to engage the projections and alternately form a steamjoint with the projections, and an exhaustspace between the block and projection, substantially as set forth.

2. The combination, with a cylinder provided with one exhaust-port and two steamports and a sliding valve, of blocks operated by the valve and adapted to alternately form a steamjoint and an exhaust-space, substantially as set forth.

3. The combination, with a sliding valve provided with depending projections in the valve-chamber, of blocks rigidly secured together and operated by the valve, said blocks being adapted to form a steam-joint with the said projections and allow a continual exhaust over themselves and the projections, and spring-rolls for holding the blocks on the valveseat, substantially as set forth.

4:. The combination, with a sliding valve provided with blocks which alternately form a steam-joint with the valve and-an exhaustspace between themselves and the valve, .of projections secured rtoythe blocks and corresponding projections secured to the valve, the whole forming bearings for sustaining the pressure on the blocks, substantially as set forth.

In testimony whereof I have signed this specification in. the presence of two subscribing witnesses.

GEORGE W. ANDERSON.

Witnesses:

MILTON M. MEWHINNEY, ISAIAH PROCTOR. 

